1. Field of the Invention
This invention relates to sanitary laminated rubber articles suitable for use as various articles with safety and sanitary property, for example, containers for foods or pharmaceutical chemicals, transporters, instruments, packaging materials and the like.
The rubber article of the present invention has very excellent properties which can be adapted to the standard test values of various official documents, required in this field, and can further satisfy the test items having lately become an important problem from the pharmaceutical standpoint and has good economical property.
2. Description of the Prior Art
As a law concerning packaging materials or instruments of food containers, there is the Food Sanitation Act, providing nonpoisonous property, tasteless property and oderless property. This sanitary property includes heat resistance and hot water resistance. The details thereof are shown in Official Notification No. 370 (December, 1962) and Official Notification No. 20 (April, 1982) of the Ministry of Health and Welfare.
High grade sanitary property and safety are required of containers for pharmaceutical chemicals from the standpoint of influences on the human body. To this end, various test methods or quality standards are provided in, for example, "11th Revision, Japanese Pharmacopoeia" (hereinafter referred to as JP 11), International Standards Organization (ISO), European Pharmacopoeia (EP) U.S. Pharmacopoeia XXI (USP), West Germany Industrial Standard DIN 58, 366-58, 368 (DIN), British Standard 3263 (BS), etc. Furthermore, test items and higher standards from medical standpoint have lately been taken into additional consideration.
As to articles for medical treatment, test methods and quality standards are provided in Official Notification Nos. 300 and 301 (standards for blood-collecting equippments and blood-transfusion sets) of the Ministry of Health and Welfare and Official Notification Nos. 442 and 413 (standards for injection cylinders) of the Ministry of Health and Welfare.
For the above described official documents are useful rubbers such as isoprene rubber (hereinafter referred to as IR), butadiene rubber (BR), ethylene-propylene rubber (EPM), ethylene-propylene-terpolymer (EPDM), isobutylene-isoprene rubber (IIR) or chlorinated rubber of IIR (CIIR) or brominated rubber of IIR (BIIR), isobutylene-isoprene-divinylbenzene terpolymer (DIIR) and the like.
As to rubber articles for foods, various techniques have been developed so as to satisfy the standards or requirements for such use, for example, a method of increasing heat resistance by mixing styrene-isoprene copolymer and polyethylene (Japanese Patent Laid-Open Publication Nos. 76939/1973 and 76940/1973); a method comprising adding tocophenol to EPDM and obtaining a laminated article for packaging a heated and sterilized food (Japanese Patent Laid-Open Publication No. 134574/1978); a rubber composition for food sanitation comprising EPDM with zinc white, a fatty acid salt of zinc and calcium oxide (Japanese Patent Publication No. 25175/1987); and a method of producing a rubber article for foods.
In the techniques of obtaining rubber articles for pharmaceutical chemicals and medical instruments, there have been proposed a method comprising adding ascorbic acid or its derivative and thus preventing formation of N-nitroso compound (Japanese Patent Publication Nos. 34262/1989 and 53696/1989); a nipple composed of BR, BIIR and natural rubber, crosslinked with an organic peroxide (Japanese Patent Publication Nos. 20650/1989); a rubber stopper comprising IR and finely powdered PE (Japanese Patent Publication Nos. 8789/1970); a rubber article for pharmaceutical chemicals, free from release of a zinc salt (Japanese Patent Publication Nos. 40257/1986) and an improved rubber stopper based on this rubber article (Japanese Patent Publication Nos. 57870/1985); and a rubber article for pharmaceutical chemicals and medical articles, comprising IIR, BII, CIIR and superhigh molecular weight PE (Japanese Patent Publication No. 55666/1989).
Furthermore, as a rubber article for pharmaceutical chemicals and medical instruments, comprising a rubber composition coated with a resin film, there are proposed a technique of laminating a vulcanized rubber with a film of polypropylene (PP) (Utility Model Publication Nos. 5751/1969 and 27753/1969); a stopper wholly coated with a fluoro resin excellent in chemical resistance (Utility Model Publication No. 17831/1970); a rubber stopper covered with a trifluoroethylene resin on a surface in contact with a medical liquor (Utility Model Publication No. 21346/1974); a process for the production of a rubber stopper, in particular, laminated with a fluoro resin film on a surface in contact with a medical liquor (Japanese Patent Publication Nos. 1355/1977, 9119/1979, 53184/1982, Japanese Patent Laid-Open Publication Nos. 272134/1986 and 23961/1990); and a rubber stopper consisting of IIR laminated with a fluoro-resin film (Japanese Patent Publication No. 3104/1988 and Utility Model Laid-Open Publication No. 47850/1980), as well known in the art.
In the known techniques, however many rubber compounding agents are studied, elution products or stripped materials occur from the rubber compounding agents or rubbers and contaminate medical liquors. Thus, it has been taken as a means for preventing an exterior medical liquor from contamination to cover a rubber article with a fluoro resin film or PE or PP resin film. However, such sanitary films of fluoro resins, PE, PP, etc. have low bonding strengths to rubber surfaces and are thus stripped readily. A higher bonding strength can be obtained by subjecting the surface of a film to a surface treatment, e.g. by corona discharge, but this is a high grade technique having an economical problem.